The biology of T-cells in allergy and asthma: beyond the TH1/TH2 concept

Complementary roles for lipid and protein allergens in triggering innate and adaptive immune systems

BACKGROUND

Recent advances in allergy research mostly focussed on two major headings: improving protein allergen purification, which is aimed towards a better characterization of IgE- and T-cell reactive epitopes, and the potential new role for unconventional innate and regulatory T cells in controlling airway inflammation. These advancements could appear to be in conflict each other, as innate T cells have a poorly-defined antigen specificity that is often directed toward nonprotein substances, such as lipids.

METHOD

To reconcile these contrasting findings, the model of cypress pollinosis as paradigmatic for studying allergic diseases in adults is suggested.

RESULTS

The biochemical characterization of major native protein allergens from undenatured pollen grain demonstrated that the most relevant substance with IgE-binding activity is a glycohydrolase enzyme, which easily denaturizes in stored grains. Moreover, lipids from the pollen membrane are implicated in early pollen grain capture and recognition by CD1(+) dendritic cells (DC) and CD1-restricted T lymphocytes. These T cells display Th0/Th2 functional activity and are also able to produce regulatory cytokines, such as IL-10 and TGF-beta. CD1(+) immature DCs expand in the respiratory mucosa of allergic subjects and are able to process both proteins and lipids.

CONCLUSION

A final scenario may suggest that expansion and functional activation of CD1(+) DCs is a key step for mounting a Th0/Th2-deviated immune response, and that such innate response does not confer long-lasting protective immunity.

Prevalence of allergies in children with complex medical problems

The aim is to determine whether there is a pattern of allergic and immune abnormalities in children with complex medical problems. The authors retrospectively studied a convenience sample of 69 children in a case management program. Of 69 children, 42 underwent immunologic investigations during the selected time frame. Forty (95%) had 1 or more allergic disorder. Cow's milk sensitivity was present in 32 (76%). Abnormal immunoglobulin levels, IgG, IgA, and IgE were found at a greater frequency than in the general pediatric population (P <.005). Lymphocyte subset percentages were decreased for B cells (CD19) and natural killer cells (CD57, CD16/56; P <.05). Presence of a gastrostomy tube, gastroesophageal reflux disease, gastric acid suppression, and chronic constipation were common and failure to thrive, developmental delay, sleep disturbance, and recurrent otitis media were present in the majority. The authors report a higher than expected prevalence of allergic and immune abnormalities in children with complex medical problems.